Heating and/or cooling systems including air-conditioning, chiller, refrigeration, and heat pump systems may include a flash tank disposed between a heat exchanger and the compressor for use in improving system capacity and efficiency. The flash tank receives liquid refrigerant from a heat exchanger and converts a portion of the liquid refrigerant into vapor for use by the compressor. Because the flash tank is held at a lower pressure relative to the inlet liquid refrigerant, some of the liquid refrigerant vaporizes, causing the remaining liquid refrigerant in the flash tank to lose heat and become sub-cooled. The resulting vapor within the flash tank is at an increased pressure and may be injected into the compressor to increase the heating and/or cooling capacity of the system.
The vaporized refrigerant from the flash tank is distributed to a medium or intermediate pressure input of the compressor. Because the vaporized refrigerant is at a substantially higher pressure than vaporized refrigerant leaving the evaporator, but at a lower pressure than an exit stream of refrigerant leaving the compressor, the pressurized refrigerant from the flash tank allows the compressor to compress this pressurized refrigerant to its normal output pressure while passing it through only a portion of the compressor.
The sub-cooled refrigerant disposed in the flash tank similarly increases the capacity and efficiency of the heat exchanger. The sub-cooled liquid is discharged from the flash tank and is sent to one of the heat exchangers depending on the desired mode (i.e., heating or cooling). Because the liquid is in a sub-cooled state, more heat can be absorbed from the surroundings by the heat exchanger, thereby improving the overall performance of the heating or cooling cycle.
The flow of pressurized refrigerant from the flash tank to the compressor is regulated to ensure that only vaporized refrigerant is received by the compressor. Similarly, flow of sub-cooled-liquid refrigerant from the flash tank to the heat exchanger is regulated to inhibit flow of vaporized refrigerant from the flash tank to the heat exchanger. Both of the foregoing situations may be controlled by regulating the flow of liquid refrigerant into the flash tank. In other words, by regulating the flow of liquid refrigerant into the flash tank, the amount of vaporized refrigerant and sub-cooled-liquid refrigerant may be controlled, thereby controlling flow of vaporized refrigerant to the compressor and sub-cooled-liquid refrigerant to the heat exchanger.